My check engine light came on with the code P0420 - "Catalyst efficiency below threshold".

Can I drive it for a week until I get a chance to fix it or should I leave it parked?

Also, from what I've read on this forum it's best to replace the 02 sensors before the cat. Should I replace the after cat or before cat sensor first? Or both at the same time?

 

Ya you can still drive it. As long as the cel isnt flashing... Id say replace both 02 sensors.. It helps if you tell us your engine type/yr, etc. Get your sensors from www.oxygensensors.com they have the best prices ive seen. if that doesn fix your problem, your cat might haven taken a crap.

 

Great thanks. Oh, and its a 2002 1.8t Quattro.

 

CAT or 2nd 02 crapped.. I wouldnt worry.. it only lets you know if emmissions are working

 

If it starts flashing then stop driving it.

 

Will Do. Thanks!

 

i have got the same issue , changed cat and pre cat sensor keep getting same code

 

it doesnt matter, not a big deal